Measuring cells of this type utilize so-called Clark-electrodes for measuring the concentration or partial pressure of gases.
In known Clark-electrode arrangements, the measuring electrode is made of a thin platinum wire which is brought up to a predetermined spacing in the electrolyte with respect to the inner surface of the diffusion membrane. In this connection, maintaining this spacing between the platinum wire point and the membrane surface is important. Any change of the spacing causes a change in the measured value and can be brought about, for example, by a mechanical loading of the diffusion membrane.
United Kingdom Pat. No. 1,200,595 discloses that this disadvantage can be improved upon by configuring the measuring electrode as an electrically conducting layer applied to the surface of the diffusion membrane facing toward the electrolyte. Since an electrolyte, the electrode material corresponding to the electrolyte and the required diffusion membrane are all determined by the measuring task, the selection of an electrode material as well as the membrane material can no longer be made alone with respect to the view point of a good adherence of the electrically-conductive metal film on the diffusion membrane. Accordingly, the possibility of combinations of electrolyte, electrode material and diffusion membrane which ensure a reliable adherence of the electrically-conducting film on the diffusion membrane is limited. Electrically-conductive layers which adhere poorly must be supported with an additionally applied porous protective membrane.